In Africa, hippos and crocs generally live in the same parts of the river – they’re like two cold war superpowers living by the doctrine of mutually assured destruction! They’re both so powerful and so well armed that they don’t really fight, since if one attacks the other, they could both end up killed. But that means that, as a biologist working on crocodiles, I’ve spent a lot of time around hippos.

When I white water rafted down the rapids of the Olifants Gorge, in Kruger National Park, South Africa, I was much more scared of the hippos in the river than I was of the crocs. Same in other African rivers I’ve worked in, including the Shire here in Malawi. But because I’ve spent so much of my life being scared of hippos, it was just an unbelievable experience on this show to get close to a huge wild bull. So close I could touch it.

This is how it happened. After the vet, Andre Uys, had netted and darted the hippo, we tracked it to a wooded area. That was super tense because we knew the hippo was in this small area, but the vegetation was so dense we couldn’t actually see it. At one point, I came around some vegetation and there was the hippo right in front of me! We all took off as fast as we could, and then we lost the hippo again. We got a local ranger, a guy named Christopher, to track it, and incredibly, he lead us right to it. By now, the sedative had started to kick in, and the hippo finally went down. Then Andre and I very, very carefully used a towel to cover its eyes, to keep it calm. Eventually, I was able to put my hands on it, and even pull up its lip to check out its huge tusk.

I’ve gotten close to hippos before – but it’s been truly terrifying. One time, I tried to measure the bite force of a hippo in a zoo in Malaysia. The zoo authorities let the cameraman and me actually go into the hippo’s enclosure, which in retrospect was probably not a good idea… We had my bite bar on a long pole, but we still had to get within about 6 feet of this massive male hippo. As we tried to get him to bite the bar, he charged us. The cameraman, a worker from the zoo and I all tried to get out of the pen as fast as we could – problem was the only exit was a small opening in the fence, about 4 feet by 4 feet. I ended up vaulting over the 8 foot fence in a fit of superhuman strength – I could actually feel the hippo’s lips against the back of my legs!